Smart doorbell



FIG. 1 is a front elevational view of a smart doorbell showing our new design;

FIG. 2 is a rear elevational view thereof;

FIG. 3 is a left side elevational view thereof;

FIG. 4 is a right side elevational view thereof;

FIG. 5 is a top plan view thereof;

FIG. 6 is a bottom plan view thereof;

FIG. 7 is a front perspective view thereof; and,

FIG. 8 is a rear perspective view thereof.

The broken lines depict portions of the smart doorbell in which the design is embodied that form no part of the claimed design. 

CLAIM The ornamental design for a smart doorbell, as shown and described. 